1. Field of the Invention
This invention relates to vehicle suspension systems for wheeled vehicles. In one of its aspects, the invention relates to a lightweight, yet rigid, trailing arm suspension for vehicles wherein the trailing arm is positioned alongside the frame and the air spring is positioned beneath the frame.
2. State of the Prior Art
Heavy-duty vehicle suspension systems are typically characterized by high-strength components which are relatively heavy. It is desirable to reduce the weight of the suspensions without loss of strength. The lower the vehicle weight, the more load the vehicle can carry or the lower the fuel cost.
Trailing arm suspensions are well known. The suspensions comprise a frame bracket which is secured to the frame of the vehicle, a trailing arm, which is usually a rigid beam, pivotably mounted at one end to the frame bracket and having an air spring mounted between the other end and the frame. An axle is mounted midway between the ends of the trailing arm.
Bird, in U.S. Pat. No. 3,547,215, issued Dec. 15, 1970, discloses a trailing arm suspension in which a square axle is mounted beneath a trailing arm through bolted upper and lower axle brackets. The axle brackets are secured to the trailing arm through rubber bushed pin connections. Shims can be provided between the bushed pins and the upper axle brackets to adjust the pinion angle of the axle. The trailing arm is mounted between the vehicle frame and the wheels, but the air spring is mounted beneath the frame, offset laterally from the longitudinal axis of the trailing arm on a cross-beam which extends between trailing arms on each side of the vehicle. The cross-beam counterbalances the moment created by the lateral offset between the air spring and the trailing arm.
Raidel, Sr., in U.S. Pat. No. 4,465,298, issued Aug. 14, 1984, discloses another example of a trailing arm suspension in which a square axle is mounted beneath a trailing arm and the air spring is offset laterally beneath the frame. In order to counterbalance the moment created by the lateral offset relationship between the air spring and the trailing arm, Raidel uses in several embodiments a torsion roll bar similar to the Bird transverse beam and in other embodiments uses a guide between the frame and the trailing arm.
It is known to use portions of a rigid trailing arm beam as a reservoir for an air spring in a trailing arm air spring suspension. See, for example:
Pointer U.S. Pat. No. 2,742,301, issued Apr. 17, 1956;
Walker U.S. Pat. No. 2,902,291, issued Sept. 1, 1959;
Weiss U.S. Pat. No. 2,903,256, issued Sept. 8, 1959; and
Norrie U.S. Pat. No. 2,913,252, issued Nov. 17, 1959.